Plasma Generating—Chemical Looping Catalyst Synthesis by Microwave Plasma Shock for Nitrogen Fixation from Air and Hydrogen Production from Water for Agriculture and Energy Technologies in Global Warming Prevention

Abstract

Simultaneous generation of plasma by microwave irradiation of perovskite or the spinel type of silica supported porous catalyst oxides and their reduction by nitrogen in the presence of oxygen is demonstrated. As a result of plasma generation in air, NO<inf>x</inf> generation is accompanied by the development of highly heterogeneous regions in terms of chemical and morphological variations within the catalyst. Regions of almost completely reduced catalyst are dispersed within the catalyst oxide, across micron‐scale domains. The quantification of the catalyst heterogeneity and evaluation of catalyst structure are studied using Scanning Electron Microscopy, Energy Dispersive X‐ray Spectroscopy and XRD. Plasma generating supported spinel catalysts are synthesized using the technique developed by the author (Catalysts; 2016; 6; 80) and BaTiO<inf>3</inf> is used to exemplify perovskites. Silica supported catalyst systems are represented as M/Si = X (single catalysts) or as M(<inf>1</inf>)/M(<inf>2</inf>)/Si = X/Y/Z (binary catalysts) where M; M(<inf>1</inf>) M(<inf>2</inf>) = Cr; Mn; Fe; Co; Cu and X, Y, Z are the molar ratio of the catalysts and SiO<inf>2</inf> support. Composite porous catalysts are synthesized using a mixture of Co and BaTiO<inf>3</inf>. In all the catalysts, structural heterogeneity manifests itself through defects, phase separation and increased porosity resulting in the creation of the high activity sites. The chemical heterogeneity results in reduced and oxidized domains and in very large changes in catalyst/support ratio. High electrical potential activity within BaTiO<inf>3</inf> particles is observed through the formation of electrical treeing. Plasma generation starts as soon as the supported catalyst is synthesized. Two conditions for plasma generation are observed: Metal/Silica molar ratio should be > 1/2 and the resulting oxide should be spinel type; represented as M<inf>a</inf>O<inf>b</inf> (a = 3; b = 4 for single catalyst). Composite catalysts are represented as {M/Si = X}/BaTiO<inf>3</inf> and obtained from the catalyst/silica precursor fluid with BaTiO<inf>3</inf> particles which undergo fragmentation during microwave irradiation. Further irradiation causes plasma generation, NO<inf>x</inf> formation and lattice oxygen depletion. Partially reduced spinels are represented as M<inf>a</inf>O<inf>b–c</inf>. These reactions occur through a chemical looping process in micron‐scale domains on the porous catalyst surface. Therefore; it is possible to scale‐up this process to obtain NO<inf>x</inf> from M<inf>a</inf>O<inf>b</inf> for nitric acid production and H<inf>2</inf> generation from M<inf>a</inf>O<inf>b–c</inf> by catalyst re‐oxidized by water. Re‐oxidation by CO<inf>2</inf> delivers CO as fuel. These findings explain the mechanism of conversion of combustion gases (CO<inf>2</inf> + N<inf>2</inf>) to CO and NO<inf>x</inf> via a chemical looping process. Mechanism of catalyst generation is proposed and the resulting structural inhomogeneity is characterized. Plasma generating catalysts also represent a new form of Radar Absorbing Material (RAM) for stealth and protection from radiation in which electromagnetic energy is dissipated by plasma generation and catalytic reactions. These catalytic RAMs can be expected to be more efficient in frequency independent microwave absorption. © 2020 by the author. Licensee MDPI, Basel, Switzerland.